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Learning and Understanding: Improving Advanced Study of Mathematics and Science in U.S. High Schools - Report of the Content Panel for Chemistry National Research Council. (1996). The Role of Scientists in the Professional Development of Science Teachers. Committee on Biology Teacher Inservice Programs. Washington, DC: National Academy Press. National Research Council. (1999). Transforming Undergraduate Education in Science, Mathematics, Engineering, and Technology. Committee on Undergraduate Science Education. Washington, DC: National Academy Press. National Science Foundation. (1996). Shaping the Future. Washington, DC: author.
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Learning and Understanding: Improving Advanced Study of Mathematics and Science in U.S. High Schools - Report of the Content Panel for Chemistry Appendix D Suggested Modifications of Examination Questions This appendix presents examples of the chemistry panel’s suggested modifications to the questions on the AP Chemistry 1999 examination, Section II, to make the questions more contextual; to probe more carefully the depth of student understanding; to seek to assess higher-order thinking skills; to require the applications of chemical principles in an enlarged or new context; and to enjoin students to link concepts to chemical systems and macroscale phenomena, not merely see chemical principles as isolated facts. In particular cases below, the original question is given, followed by its suggested modification. AP CHEMISTRY 1999, SECTION II, PART A, QUESTION 1 Original Question NH3(aq) + H2O(l) ↔ (doubled-headed arrow) NH4+(aq) + OH-(aq) In aqueous solution, ammonia reacts as represented above. In 0.0180 M NH3(aq) at 25 oC, the hydroxide ion concentration [OH-] is 5.60 x 10-4 M. In answering the following, assume that temperature is constant at 25 oC and that volumes are additive. Write the equilibrium-constant expression for the reaction represented above. Determine the pH of 0.0180 M NH3(aq). Determine the value of the base ionization constant, Kb, for NH3(aq). Determine the percent ionization of NH3 in 0.0180 M NH3(aq). In an experiment, a 20.0 mL sample of 0.0180 M NH3(aq) was placed in a flask and titrated to the equivalence point and beyond using 0.0120 M HCl(aq). Determine the volume of 0.0120 M HCl(aq) that was added to reach the equivalence point. Determine the pH of the solution in the flask after a total of 15.0 mL of 0.0120 M HCl(aq) was added. Determine the pH of the solution in the flask after a total of 40.0 mL of 0.0120 M HCl(aq) was added. (SOURCE: CEEB, 1999b, p. 42)
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Learning and Understanding: Improving Advanced Study of Mathematics and Science in U.S. High Schools - Report of the Content Panel for Chemistry Suggested Modification The panel would suggest leaving much of question 1 alone, although it could stand to be condensed somewhat. As written, it tests the student’s fundamental understanding of Kb, buffers, and titration stoichiometry. One or more of the following additional questions might be added: Sketch a titration curve for part (e) using the information from (b), (c), and (d). and/or Compare the base strength and give the rationale for strength based on the type of site and associated structure for one or two other more obscure bases, given their respective Kb’s. AP CHEMISTRY 1999, SECTION II, PART A, QUESTION 2 Original Question Answer the following questions regarding light and its interactions with molecules, atoms, and ions. The longest wavelength of light with enough energy to break the Cl-Cl bond in Cl2(g) is 495 nm. Calculate the frequency, in s-1, of the light. Calculate the energy, in J, of a photon of the light. Calculate the minimum energy, in kJ mol-1, of the Cl-Cl bond. A certain line in the spectrum of atomic hydrogen is associated with the electronic transition in the H atom from the sixth energy level (n = 6) to the second energy level (n = 2). Indicate whether the H atom emits energy or whether it absorbs energy during the transition. Justify your answer. Calculate the wavelength, in nm, of the radiation associated with the spectral line. Account for the observation that the amount of energy associated with the same electronic transition (n = 6 to n = 2) in the He+ ion is greater than that associated with the corresponding transition in the H atom. (SOURCE: CEEB, 1999b, p. 43) (NOTE: On the exam, students were asked to answer either this question or the next question concerning reaction rates, but not both.) Suggested Modification A question containing some of the information assessed in the original version of Question 2 but considerably extended might look like this. This question now relates to a chlorofluorocarbon compound known as CFC-12 or Freon-12.
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